rwsem: no need for explicit signed longs

Change explicit "signed long" declarations into plain "long" as suggested
by Peter Hurley.

Signed-off-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Reviewed-by: Michel Lespinasse <walken@google.com>
Signed-off-by: Michel Lespinasse <walken@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>